Method, device, and system for adapting distance protection against reactance effect due to remote infeed and fault resistance

Abstract

The present disclosure relates to a method for controlling a distance protection system, as well as a respective device and system for performing the method. Measurements are received. The measurements comprise current and/or voltage measurements at a first position along a transmission line for an electrical power system. A first impedance is computed from the received measurements. A fault location is determined from the computed first impedance and a first impedance boundary. Responsive to the determined fault location, a second impedance is computed. The fault location is redetermined from the computed second impedance and the first impedance boundary. The distance protection system is controlled based on the determined fault location or the re-determined fault location.

What is claimed is: 
     
       1. A method for controlling a distance protection system, the method comprising:
 receiving, measurements comprising current and/or voltage measurements at a first position along a transmission line for an electrical power system; 
 computing a first impedance from the received measurements; 
 determining a fault location from the computed first impedance and a first impedance boundary; 
 computing, responsive to the determined fault location, a second impedance; 
 re-determining the fault location from the computed second impedance and the first impedance boundary; and 
 controlling the distance protection system from the determined fault location or the re-determined fault location, 
 wherein computing the second impedance comprises: 
 determining a homogeneity of the electrical power system, from at least one impedance of an equivalent model of a two-port equivalent across the transmission line and a line impedance of the transmission line; and 
 approximating, when the electrical power system is determined to be homogeneous, the second impedance from the at least one impedance of the equivalent model of the two-port equivalent across the transmission line and the line impedance of the transmission line; or 
 estimating, when the electrical power system is determined to be non-homogeneous, the fault location from the measurements received at the first position, the at least one impedance of the equivalent model of the two-port equivalent across the transmission line, and the line impedance of the transmission line; and 
 computing the second impedance from the estimated fault location. 
 
     
     
       2. The method of  claim 1 , further comprising re-determining the fault location from the computed first impedance and a second impedance boundary. 
     
     
       3. The method of  claim 2 , wherein the second impedance boundary is computed from the measurements obtained before a fault at the fault location occurs. 
     
     
       4. The method of  claim 2 , wherein the second impedance boundary is computed from at least one impedance of an equivalent model of a two-port equivalent across the transmission line. 
     
     
       5. The method of  claim 4 , wherein the equivalent model of the two-port equivalent across the transmission line is estimated and/or updated from the measurements obtained before a fault at the fault location occurs. 
     
     
       6. The method of  claim 2 , wherein the second impedance boundary is computed from a line impedance of the transmission line. 
     
     
       7. The method of  claim 2 , wherein the first impedance boundary is indicative of a first physical distance being a distance between the first position and a second position along the transmission line. 
     
     
       8. The method of  claim 7 , further comprising determining, when the computed first impedance is inside of the first impedance boundary, the fault location is inside of the first physical distance. 
     
     
       9. The method of  claim 8 , wherein the determining the fault location from the computed first impedance and the first impedance boundary comprises determining whether the computed first impedance is inside of the first impedance boundary. 
     
     
       10. The method of  claim 7 , wherein the re-determining the fault location from the computed first impedance and the second impedance boundary comprises determining whether the computed first impedance is inside of the second impedance boundary. 
     
     
       11. The method of  claim 10 , further comprising determining, when the computed first impedance is outside of the second impedance boundary, the fault location is outside of the first physical distance. 
     
     
       12. The method of  claim 7 , wherein the re-determining the fault location from the computed second impedance and the first impedance boundary comprises determining whether the computed second impedance is inside of the first impedance boundary. 
     
     
       13. The method of  claim 12 , further comprising determining, when the computed second impedance is inside of the first impedance boundary, the fault location is inside of the first physical distance. 
     
     
       14. The method of  claim 7 , wherein the determining the fault location from the computed first impedance and the first impedance boundary comprises determining whether the computed first impedance is inside of the first impedance boundary. 
     
     
       15. The method of  claim 1 , wherein the determining the fault location from the computed first impedance and the first impedance boundary comprises determining whether the computed first impedance is inside of the first impedance boundary. 
     
     
       16. A device for controlling a distance protection system comprising a distance protection device located at a first position along a transmission line for an electrical power system, the device comprising a processor being configured to:
 receive measurements comprising current and/or voltage measurements at a first position along a transmission line for an electrical power system; 
 compute a first impedance from the received measurements; 
 determine a fault location from the computed first impedance and a first impedance boundary; 
 compute, responsive to the determined fault location, a second impedance; 
 re-determine the fault location from the computed second impedance and the first impedance boundary; and 
 control the distance protection system from the determined fault location or the re-determined fault location, 
 wherein compute the second impedance comprises: 
 determining a homogeneity of the electrical power system, from at least one impedance of an equivalent model of a two-port equivalent across the transmission line and a line impedance of the transmission line; and 
 approximating, when the electrical power system is determined to be homogeneous, the second impedance from the at least one impedance of the equivalent model of the two-port equivalent across the transmission line and the line impedance of the transmission line; or 
 estimating, when the electrical power system is determined to be non-homogeneous, the fault location from the measurements received at the first position, the at least one impedance of the equivalent model of the two-port equivalent across the transmission line, and the line impedance of the transmission line; and 
 computing the second impedance from the estimated fault location. 
 
     
     
       17. The device of  claim 16 , wherein the processor is further configured to re-determine the fault location from the computed first impedance and a second impedance boundary,
 wherein the second impedance boundary is computed from at least one of the measurements obtained before a fault at the fault location occurs, at least one impedance of an equivalent model of a two-port equivalent across the transmission line, or a line impedance of the transmission line. 
 
     
     
       18. An electrical power system comprising a transmission line and the device of  claim 16 .